Techniques that extract a text region from an image have been known. For example, the technique that extracts regions of the same color and being connected as a text region is disclosed in Non Patent Literature 1 below. Another method is that, for a region where the same colors are connected, calculates an aspect ratio f1 of a circumscribing rectangle and a ratio f2 of the area of the same color region to the area of the circumscribing rectangle and determines a rectangular region having f1 and f2 in a specified range as a text region. Yet another method is line determination that determines a plurality of rectangular regions having such characteristics and continuously arranged in a line as a text region.